210 ON THE. NAIADES, 



cies. 1 know of no other species which has its lateral teeth so much 

 elevated, following, as they do, the widened margin of the valve. The 

 cardinal teeth are generally double in the left valve, but not always. 

 They will always be found to be compressed in both valves, and gene- 

 rally more elevated in the right. The nacre is so very thin as to be 

 diaphanous, and the play of iridescent colours is very beautiful. As 

 the individual advances in age the marks of growth form large wrin- 

 kles, and it then becomes more cylindrical. 



Unio Kirtlandianus. Plate XIV. fig. 41 



O" 



Testa subrotundd, compressd ; valvidis crassis ; natibits subprominentibus ; epi- 

 dtrinide circa nates luted, juxta marginem fused ; radiis interruptis ; dentibus 

 cardmalibus subcrassis, lateralibus subcurvis brevibusque ; margarita albd et iri- 

 descente. 



4. 



Shell rather round, compressed ; valves thick ; beaks somewhat elevated ; epidermis 

 yellowish about the beaks, brown towards the margin ; rays interrupted ; cardinal teeth 

 rather thick ; lateral teeth short and slightly curved ; nacre pearly white and iridescent. 



Hab. Mahoning, Ohio. J. P. Kirtland, M.D. 



My Cabinet. 



Cabinet of P. H. Nicklin. 



Diam. 1, Length 2, Breadth 2-3 inches. 



Shell rather round, compressed ; substance of the shell thick, some- 

 what thinner behind ; beaks rather elevated ; ligament rather short and 

 thick ; epidermis wrinkled, dark brown, smooth and yellowish in the 

 region of the beaks ; interrupted rays pass from the beaks and are very 

 visible over the umbones, but are lost in the wrinkles before they reach 

 the margin ; cardinal teeth rather thick ; lateral teeth short, thick and 

 slightly curved ; posterior and anterior cicatrices both distinct ; dorsal 

 cicatrices situated on the under side of the cardinal teeth ; cavity of 

 the shell flat and shallow ; cavity of the beaks rather deep and angu- 

 lated ; nacre pearly white and iridescent. 



Remarks. — I owe this new species to the kindness of Dr Kirtland of 



